// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
using System.Collections.Generic;
using System.Collections.ObjectModel;

namespace Google.ProtocolBuffers.Collections {

  /// <summary>
  /// Utility non-generic class for calling into Lists{T} using type inference.
  /// </summary>
  public static class Lists {

    /// <summary>
    /// Returns a read-only view of the specified list.
    /// </summary>
    public static IList<T> AsReadOnly<T>(IList<T> list) {
      return Lists<T>.AsReadOnly(list);
    }

    public static bool Equals<T>(IList<T> left, IList<T> right) {
      if (left == right) {
        return true;
      }
      if (left == null || right == null) {
        return false;
      }
      if (left.Count != right.Count) {
        return false;
      }
      IEqualityComparer<T> comparer = EqualityComparer<T>.Default;
      for (int i = 0; i < left.Count; i++) {
        if (!comparer.Equals(left[i], right[i])) {
          return false;
        }
      }
      return true;
    }

    public static int GetHashCode<T>(IList<T> list) {
      int hash = 31;
      foreach (T element in list) {
        hash = hash * 29 + element.GetHashCode();
      }
      return hash;
    }
  }

  /// <summary>
  /// Utility class for dealing with lists.
  /// </summary>
  public static class Lists<T> {

    static readonly ReadOnlyCollection<T> empty = new ReadOnlyCollection<T>(new T[0]);

    /// <summary>
    /// Returns an immutable empty list.
    /// </summary>
    public static ReadOnlyCollection<T> Empty {
      get { return empty; }
    }

    /// <summary>
    /// Returns either the original reference if it's already read-only,
    /// or a new ReadOnlyCollection wrapping the original list.
    /// </summary>
    public static IList<T> AsReadOnly(IList<T> list) {
      return list.IsReadOnly ? list : new ReadOnlyCollection<T>(list);
    }
  }
}
